The answer is B. The number of stomata is more on the lower surface of the leaf. Carbon dioxide enters the leaves through the stomata. In the leaves, it is used in the photosynthesis and converted into oxygen and glucose. Since the energy of Sunlight is important for the photosynthesis, stomata must be opened during the day. So, to avoid direct Sunlight and thus cause leaves dehydration, the number of stomata is more on the lower surface of the leaf.
